This invention relates to mammary prostheses and more particularly to a novel contracture resistant breast implant.
Breast implants or prostheses used for breast augmentation and for breast reconstruction generally include a soft, flexible plastic envelope containing a cohesive gelatinous material. The envelope can for example, be of a semi-spherical, semi-teardrop or semi-oval shape. Other selected shapes can also be used depending upon the particular needs of a patient. Generally, the envelope is not filled to capacity and the quantity of gel provided enables the contour or shape of the envelope to be easily indented, deformed or compressed.
A common technique for implanting the prosthesis is to make an incision at the base of the breast on the inframammary fold under the curve of the breast. A pocket, either directly below the breast or below the pectoralis muscle is made by working through the incision. The pocket can be formed behind the breast tissue or underneath the muscle. The prosthesis is thus placed in this pocket and the incision is closed.
Following implantation, healing scar tissue forms around the implant substantially encapsulating the implant. This scar tissue capsule frequently contracts the pocket in which the implant is disposed. Such contracture exerts external pressure on the implant that deforms the semispherical, semi-teardrop or oval shape of the prosthesis. In extreme cases of scar tissue contracture, the scar tissue capsule will cause the prosthesis to contract to a geometric configuration which holds the most volume in the least available space, such as a spherical shape. This condition is known as "spherical contracture".
Scar tissue contracture causes the gel within the implant to become pressurized thereby forming a local rigidification under the breast, with a resulting firmness that is undesirable and often painful. In addition, the initial shape of the augmented or reconstructed breast may become more spherical because of the capsular induced contraction of the implant. The change in shape of the breast to an undesirable spherical form is the most common complication of breast implant surgery, occurring in up to 65% of cases reported in recent studies.
U.S. Pat. No. 4,264,990 to Hamas, for a mammary prosthesis attempts to deal with the phenomena of capsular contractures of an implant by providing the implant with a backing having spaces into which a curable rigidifying material is provided. The curing and rigidification takes place after implantation and the rigidified backing is intended to prevent scar tissue contracture of the prosthesis to obviate hardening of the implant. The Hamas device thus requires a special treatment process of the prosthesis prior to implantation. The treatment process requires skill and the need for additional preparation time of the prosthesis. The disclosed use of a material which is intended to cure within a patient to provide a desirable rigidity is accompanied by a risk that such material may not cure properly, or through inadvertence, may leak or otherwise become unconfined from the implant causing adverse affects to the patient.
U.S. Pat. No. 4,298,997 to Rybka, also deals with the problems of fibrous capsular contractures in silicone breast implants. Rybka suggests that a spacer device in the form of a thin silicone sheet be adhered to the implant to provide a base for the implant. An annular strip of Dacron felt is secured to the periphery of the disk to permit ingrowth of tissue and provide an anchor for the scar tissue capsule. The silicone sheet and annular DACRON (polyethylene terephthalate) Dacron band do not function as a reinforcement for preventing contracture of an implant. The Rybka device thus relies on a controlled growth of scar tissue to form an anchor for an implant in order to limit the constricting affect of such scar tissue. However, the presence of DACRON, even in small amounts, has been shown to cause excessive scar tissue formation in the entire capsule surrounding the implant, thus frequently producing an undesirable degree of spherical contracture.
It is thus desirable to provide a mammary prosthesis which does not allow scar tissue contracture to occur, does not require special structural preparation before implantation, and does not rely on a particular direction of scar tissue growth to limit the constricting effect of such scar tissue.